The present invention relates to an alarm electronic timepiece for displaying time by an hour hand, minute hand and second hand, and more particularly to an alarm electronic timepiece having means for preventing mis-operation of the stepping motor caused by a drop in the battery voltage when an alarm sound is being generated.
The conventional alarm electronic timepiece having an hour hand, minute hand and second hand is provided with an electronic buzzer serving as a sound generating means and a stepping motor serving as a hand stepping means. Since the electronic buzzer consumes a comparatively large current of several to ten several mA in the sound generating state, the terminal voltage of the battery drops under the influence of the internal resistance of the battery. If the stepping motor is driven in this condition, there is the likelihood that the stepping motor will mis-operate and cease stepwise rotation. Therefore it is necessary to shift the signal for driving the electronic buzzer from the signal for driving the stepping motor (hereafter referred to as a hand stepping pulse) beforehand or it is necessary to prohibit the electronic buzzer driving signal when both signals come into conflict and occur at the same moment. The former method is effective in the case of a single sound which is regularly repeated, however, it is not effective in the case of a dampened sound of comparatively long period which is irregularly repeated as shown in FIG. 1. In the latter method, the alarm sound as shown in FIG. 1 is periodically interrupted so that the desired sound would not be produced if the buzzer driving signal were inhibited at each occurrence of the hand stepping pulse.